More storms on the way as teams search debris of devastated city

Rescue teams in Missouri were trying yesterday to find more trapped survivors and pull those who did not survive from the rubble of a Walmart warehouse that was destroyed by Sunday's tornado.

With more storm activity expected this morning, emergency-service crews converged on Joplin from across the region to respond to the disaster, the scale of which was still hard for some to grasp.

The most urgent searches were focused on the Walmart store, a nearby Home Depot and apartment buildings that had been severely hit. Officials put the death toll so far at 117 – the deadliest recorded twister in the United States for more than six decades.

Late Monday, seven bodies were pulled from under one of the concrete slabs that had been part of a wall in the Walmart store. Meanwhile, 1,500 people were reported missing; phone coverage was limited.

Six of the victims died at St John's Hospital, which took a direct hit from the twister. Five of those were in the intensive-care ward and on ventilators that stopped working when the tornado cut the power and knocked out emergency generators. Frantic efforts by the staff to work the ventilators by hand were in vain.

"We're hoping to find more folks, that's why we're doing these searches," Keith Stammer, the emergency-management director of Jasper County, said at an outdoor press conference. The head of the Federal Emergency Management Agency, Craig Fugate, said his teams would stay for "the long haul, not just for the response". Barack Obama will visit on Sunday, after his European visit.

About a third of Joplin had been cordoned off to keep out sightseers and allow the rescue teams – some with dogs trained to sniff out dead bodies – to comb through destroyed homes, offices, shops and apartment buildings. Those already searched were marked with a spraypainted X, reminding some of the searches in New Orleans neighbourhoods after Hurricane Katrina.

The horror of tornado's assault on Joplin, home to 50,000 people, was still unfolding as families searched desperately for missing loved ones and rescue workers and volunteers faced the trauma of having to dig out the victims' bodies. Around one home, teams were looking for an 18-month-old boy who was torn from his parents' grasp as the tornado passed on Sunday evening. "We don't want a bulldozer to find the boy four months from now," said Chris Moreno, who was in charge of first aid outside the ruined St John's hospital.

Also still missing was a teenager identified as Will Norton, who was sucked through the sunroof of his father's car as they drove home from school. His father is alive and in stable condition. An aunt, Sarah Norton, told CBS News that she had spoken to the man about what happened. "He had his arms around Will when they started flipping and Will's seatbelt snapped and he flew through the sunroof," she said.

The staff at the hospital did all they could in the few minutes they had before the tornado hit, but its power was too much. Nurses recalled hearing the roof rip off while glass from imploded windows flew everywhere, cutting nearly everyone inside. When it was over, nearly everyone was splattered with blood and the IV tubes had been ripped out of patients' arms.

Some of those in the emergency room had been sucked through the doors to the car park outside.